1. Field
One or more embodiments of the present invention relate to a secondary battery.
2. Description of the Related Art
In general, unlike primary batteries that are not designed to be recharged, secondary batteries are rechargeable (i.e., they may be recharged and discharged). According to the type of external device for which the battery power is used, a secondary battery may be used as a single battery, or a plurality of secondary batteries coupled to form a single battery module.
Recently, demand for a high-output and high-capacity battery has increased because batteries are now used in large sized transportation vehicles, such as hybrid cars, as well as used in small-sized electronic devices, such as cell phones and laptop computers.
In order to comply with such demand, batteries having low resistance have been designed by thin-filming an electrode plate, but the material used has material characteristic limits. Thus, methods of mixing active carbon, which can be a capacitor material, with an active material have been developed to overcome the limit of the materials. However, when active carbon with a large specific surface area is used in a battery, high-rate characteristics of the battery may be improved, but a capacity of the battery is lower than a battery formed of a lithium transition metal oxide.
In this regard, a lithium transition metal oxide, such as a lithium cobalt oxide, an oxide having an olivine crystalline structure, or a lithium nickel cobalt manganese oxide, is used. However, when the lithium transition metal oxide is used in a secondary battery for a large-sized transportation vehicle, such as a hybrid car, characteristics of electric power may still be deteriorated because a possibility of heat generation may be too high or a capacity may be too low due to destruction of the structure of the secondary battery when it is overcharged.